The osmtpd API is an event-based C programming interface for writing OpenSMTPd filters.

isync/mbsync is a command-line tool for two-way synchronization of mailboxes. Currently Maildir and IMAP are supported types.

This package provides a tool to extract, recover and undelete email messages from Outlook Express .dbx files.

Pigeonhole adds support for the Sieve language (RFC 5228) and the ManageSieve protocol (RFC 5804) to the Dovecot e-mail server.

Sieve is a language for filtering incoming mail. Messages can be forwarded or sorted into separate folders. Unwanted messages can be rejected or discarded, and, when the user is not available, the Sieve interpreter can send an automated reply.

Sieve is meant to be simple, extensible, and system-independent. The intention is to make it impossible to write anything more complex (and dangerous) than simple mail filters. Unlike most other mail filtering script languages, Sieve does not allow users to execute arbitrary programmes.

Through the ManageSieve protocol, users can remotely manage their Sieve scripts without needing file system access. The server accepts only valid scripts to prevent embarrassing errors later on.

Bogofilter is a mail filter that classifies mail as spam or ham (non-spam) by a statistical analysis of the message's header and content (body). The program is able to learn from the user's classifications and corrections. It is based on a Bayesian filter.

Email::Abstract provides module writers with the ability to write simple, representation-independent mail handling code.

Exim is a message transfer agent (MTA) developed at the University of Cambridge for use on Unix systems connected to the Internet. In style it is similar to Smail 3, but its facilities are more general. There is a great deal of flexibility in the way mail can be routed, and there are extensive facilities for checking incoming mail.

Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules including regular expressions, statistical analysis and custom services such as URL black lists. Each message is analysed by Rspamd and given a spam score.

Mlmmj is a simple and slim mailing list manager (MLM) inspired by ezmlm. It works with many different Mail Transport Agents (MTAs) and is simple for a system administrator to install, configure and integrate with other software. As it uses very few resources, and requires no daemons, it is ideal for installation on systems where resources are limited. Its features include:

1. Archive, Custom headers / footer,

2. Fully automated bounce handling (similar to ezmlm),

3. Complete requeueing functionality, Moderation functionality, Subject prefix,

4. Subscribers only posting, Regular expression access control,

5. Functionality to retrieve old posts, Web interface, Digests,

6. No-mail subscription, VERP support,

7. Delivery Status Notification (RFC1891) support,

8. Rich and customisable texts for automated operations.

This package provides an Emacs-based interface to the Notmuch mail system.

This Python module can be used to generate and parse RFC 5451/7001/7601 Authentication-Results email headers. It supports extensions such as:

• RFC 5617 DKIM/ADSP

• RFC 6008 DKIM signature identification (header.b)

• RFC 6212 VBR

• RFC 6577 SPF

• RFC 7281 Authentication-Results registration for S/MIME

• RFC 7293 The Require-Recipient-Valid-Since header field

• RFC 7489 DMARC

• ARC (draft-ietf-dmarc-arc-protocol-08)

Blists is a web interface to mailing list archives that works off indexed mbox files. There are two programs: bindex and bit. bindex generates or updates the index file (incremental updates are supported). bit is a CGI/SSI program that generates web pages on the fly. Both programs are written in C and are very fast.

This package provides a CLI application to execute scripts on IMAP mailbox changes (new/deleted/updated messages) using IDLE and it is mostly compatible with the configuration of imapnotify made with Python.

This package takes your 48x48x1 portrait image and compresses it.

Email::Sender replaces the old and sometimes problematic Email::Send library.

This package provides a CLI application to execute scripts on IMAP mailbox changes (new/deleted/updated messages) using IDLE and it is mostly compatible with the configuration of imapnotify made with Python.

MHonArc is a Perl mail-to-HTML converter. MHonArc provides HTML mail archiving with index, mail thread linking, etc; plus other capabilities including support for MIME and powerful user customization features.

The mblaze message system is a set of Unix utilities for processing and interacting with mail messages which are stored in maildir folders.

Its design is roughly inspired by MH, the RAND Message Handling System, but it is a complete implementation from scratch.

mblaze is a classic command line MUA and has no features for receiving or transferring messages; you can operate on messages in a local maildir spool, or fetch your messages using fdm(1), getmail(1), offlineimap(1), or similar utilities, and send it using dma(8), msmtp(1), sendmail(8), as provided by OpenSMTPD, Postfix, or similar.

mblaze operates directly on maildir folders and doesn't use its own caches or databases. There is no setup needed for many uses. All utilities have been written with performance in mind. Enumeration of all messages in a maildir is avoided unless necessary, and then optimized to limit syscalls. Parsing message metadata is optimized to limit I/O requests. Initial operations on a large maildir may feel slow, but as soon as they are in the file system cache, everything is blazingly fast. The utilities are written to be memory efficient (i.e. not wasteful), but whole messages are assumed to fit into RAM easily (one at a time).

Sendmail is a mail transfer agent (MTA) originally developed by Eric Allman. It is highly configurable and supports many delivery methods and many transfer protocols.

Mew (Messaging in the Emacs World) is a user interface for text messages, multimedia messages (MIME), news articles and security functionality including PGP, S/MIME, SSH, and SSL.

This package provides Python bindings to use the Notmuch mail indexing and search library.

The mailmanclient library provides official Python bindings for the GNU Mailman 3 REST API.

dovecot-libsodium-plugin provides a libsodium password hashing scheme (such as scrypt) plug-in for Dovecot.

Python module that implements DKIM (DomainKeys Identified Mail) email signing and verification (RFC6376). It also provides helper scripts for command line signing and verification. It supports DKIM signing/verifying of ed25519-sha256 signatures (RFC 8463). It also supports the RFC 8617 Authenticated Received Chain (ARC) protocol.